src: avoid copying BaseObjectPtrs in loop

While copying BaseObjectPtrs is cheap, it is not a no-op, so it is best
to iterate over references to BaseObjectPtrs only.

PR-URL: #44270
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

src/node_messaging.cc

@@ -349,7 +349,7 @@ class SerializerDelegate : public ValueSerializer::Delegate {
       std::vector<BaseObjectPtr<BaseObject>> nested_transferables;
       if (!host_objects_[i]->NestedTransferables().To(&nested_transferables))
         return Nothing<bool>();
-      for (auto nested_transferable : nested_transferables) {
+      for (auto& nested_transferable : nested_transferables) {
         if (std::find(host_objects_.begin(),
                       host_objects_.end(),
                       nested_transferable) == host_objects_.end()) {